The present invention relates to a device for the power-assisted steering of a vehicle, which comprises control means acting on steering means, the said control means having a transmission element such as a steering column in two parts which are capable of limited relative angular displacement on either side of a neutral position under the action of the said control means, the said parts being connected to one another by elastic means for returning the parts to the neutral position, and assistor means which, in response to this angular displacement between the parts, are operable to act on the steering means in the same direction as the control means. In particular, the invention relates to such a device in which the said assistor means comprise a hydraulic power source, a hydraulic jack acting on the steering means, and a hydraulic distributor interposed between the hydraulic power system and the jack, the said distributor comprising stator means which are connected to the hydraulic power source and the hydraulic jack, and two corresponding rotors which are respectively integral in rotation with the two relatively movable parts and which are provided with passages for hydraulic fluid.
Usually, the elastic means for returning the two parts of the transmission element to the neutral position consist of a torsion bar interconnecting the parts; this torsion bar may extend inside the parts, which are then made hollow for this purpose.
The effect of forming the parts as hollow bodies is to increase the radial bulk of the unit. Moreover, it is necessary to carry out an adjustment so that, in the neutral position of elastic return, defined by the torsion bar, the juxtaposition of the hydraulic passages in the rotors is perfectly neutral so that the assistor means has in this position no effect on the steering.
It is an object of the present invention to provide a device for the power-assisted steering of a vehicle, of the kind referred to above, which does not have these disadvantages.